Such an apparatus is in particular used in infusion or dialysis technology in order to supply a fluid and introduce it metered into a patient, wherein peristaltic pumps and syringe pumps are predominantly used in this field. Also piston pumps may advantageously be used, as U.S. Pat. No. 7,887,308 B2 for example discloses. With a piston pump it is possible to achieve a high delivery accuracy also in the case of large delivery volumes, wherein fluid is sucked in from an exchangeable storage tank.